In communication systems (both terminal and base station infrastructure), surface acoustic wave (SAW) filters and resonators are widely used. For the next generation wireless communication of 5G new radio (NR), there is growing demand for higher operating frequency, lower Insertion loss, higher transmitting power, and/or wider channel bandwidth. New piezoelectric materials or structures are desirable to support the growing demand for higher frequency and wider channel bandwidth. A high electromechanical coupling coefficient for SAW filters is typically desirable. As the transmitting power increases, the durability of the SAW device deteriorates. Therefore, it may be useful to increase the durability for a higher operating frequency and higher transmitting power.
Scandium-doped aluminum nitride (ScAlN) films have been attempted due to their high piezoelectricity, high thermal conductivity, and relatively high acoustic wave velocity. One such structure is described in “High Q surface acoustic wave resonators in 2-3 GHz range using ScAlN-single crystalline diamond structure” by Hashimoto et al. (Conf.: Ultrasonics Symposium (IUS), 2012 IEEE International), herein expressly incorporated by reference in its entirety.
Similarly, another such structure is described in “Surface acoustic wave propagation characteristics of ScAlN/diamond structure with buried electrode” by Zhang et al. (Piezoelectricity Acoustic Waves and Device Applications (SPAWDA) 2014 Symposium on, pp. 271-274, 2014), herein expressly incorporated by reference in its entirety.
These structures have been explored but have not been adequate to address the specific challenges as described herein.